When you begin to create your own website, you should already be thinking of how to get your pages on the first part of search engine results. To do this, you need to come up with a good strategy for search engine optimization.
Part of this is doing keyword research to find out what words you should be ranking for. Do not go for keywords that consist of just one or two words because these are very competitive and will not let you break through to the first top 5 ranks. There are websites which are considered the authority for certain keywords because they have been around for such a long time. These sites would usually also have SEO experts working for them so it will be really hard for you to beat their rankings.
What you need to do when you create your website is to figure out what you want to put in it. Afterwards, you can find keywords from tools like Traffic Travis and Market Samurai. You just fill in the fields with the keywords that you would like to rank for and the software will provide you with details on how many searches each keyword receives, who your competitions are, and how you would benefit if you got the first rank for that keyword.
If you are doing the research on this manually, you should decide on a couple o things before deciding on a keyword to have your page optimized for. You need to see how many searches each keyword gets every month. Aim for the ones that get the highest. The problem with this is that the competition tends to be greater. But still if you search hard enough you will find those that are often searched but the competition is low. Be patient and persevering when trying to find this.
After you have discovered a keyword that has a high volume of searches, find out the number of phrase matches for this keyword. It will help you to figure out how much competition you have.
When all this is done, go on Google and look at the first 10 results that you get for that keyword. I personally use the Firefox plug-in called SEOQuake to help me. You are trying to find the page rank of these sites on the top 10. If you find some PR0s to PR4s, it means that the sites are quite easy to compete with given that you have a good plan for on-page SEO and a lot of good quality back links. If the sites have higher PR, you should still try to go on the top 20.